Some materials, such as coffee, milk, or marble, have a soft translucent aspect because of subsurface scattering. Light enters them and gets scattered several times before leaving in a different place. A full representation of subsurface-scattering effects in illumination simulation is computationally expensive. The main difficulty comes from multiple scattering events. The high number of events increases the results' uncertainty, requiring more computation time. However, a strong correlation exists between the surface effects of multiple scattering and the effects after just two scattering events. This knowledge can help accelerate multiple-scattering effects. In particular, researchers have exploited this knowledge to provide a model and implementation for fast computation of double-scattering events using a precomputed density function stored compactly.